You are mistaken, this is not a myth. Synchronous digital chips have a clock with a fixed frequency, and their working is fixed. So if it works, a chip perform exactly the same, regardless of age. If something's slower, it's software or pheripherals. Probably software (and that's why some people are so upset: hardware is getting faster, observed performance keeps degrading. I have to wait 10 minutes for my computer before I can start working, every day).